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מבוא
התקשרות חוזרת היא כלי רב עוצמה להתאמה אישית של ההתנהגות של מודל Keras במהלך אימון, הערכה או מסקנות. דוגמאות כוללות tf.keras.callbacks.TensorBoard
לדמיין התקדמות האימונים ותוצאות עם TensorBoard, או tf.keras.callbacks.ModelCheckpoint
תקופתי תשמור את המודל במהלך האימונים.
במדריך זה תלמדו מהי התקשרות חוזרת של Keras, מה היא יכולה לעשות וכיצד תוכלו לבנות משלכם. אנו מספקים כמה הדגמות של יישומי התקשרות חוזרים פשוטים כדי להתחיל.
להכין
import tensorflow as tf
from tensorflow import keras
סקירה כללית על התקשרויות חוזרות של Keras
כל התקשרות חזרה מכל מחלקה keras.callbacks.Callback
בכיתה, ואת לדרוס קבוצה של שיטות שנקרא בשלבים שונים של אימונים, בדיקות, וחיזוי. התקשרויות חוזרות שימושיות כדי לקבל תצוגה על המצבים הפנימיים והסטטיסטיקות של המודל במהלך האימון.
אתה יכול להעביר רשימה של התקשרות חזרה (כמו מילת מפתח הטיעון callbacks
) לשיטות המודל הבאות:
סקירה כללית של שיטות התקשרות חוזרת
שיטות גלובליות
on_(train|test|predict)_begin(self, logs=None)
התקשר בתחילת fit
/ evaluate
/ predict
.
on_(train|test|predict)_end(self, logs=None)
התקשר בסוף fit
/ evaluate
/ predict
.
שיטות ברמת אצווה לאימון/בדיקה/ניבוי
on_(train|test|predict)_batch_begin(self, batch, logs=None)
נקרא ממש לפני עיבוד אצווה במהלך אימון/בדיקה/ניבוי.
on_(train|test|predict)_batch_end(self, batch, logs=None)
נקרא בתום אימון/בדיקה/חיזוי אצווה. בתוך שיטה זו, logs
הוא dict המכיל את תוצאות המדדים.
שיטות ברמת עידן (אימון בלבד)
on_epoch_begin(self, epoch, logs=None)
נקרא בתחילת תקופה במהלך אימון.
on_epoch_end(self, epoch, logs=None)
נקרא בסוף תקופה במהלך אימון.
דוגמה בסיסית
בואו נסתכל על דוגמה קונקרטית. כדי להתחיל, הבה נייבא tensorflow ונגדיר מודל פשוט של Sequential Keras:
# Define the Keras model to add callbacks to
def get_model():
model = keras.Sequential()
model.add(keras.layers.Dense(1, input_dim=784))
model.compile(
optimizer=keras.optimizers.RMSprop(learning_rate=0.1),
loss="mean_squared_error",
metrics=["mean_absolute_error"],
)
return model
לאחר מכן, טען את נתוני ה-MNIST לאימון ובדיקה מ-Keras datasets API:
# Load example MNIST data and pre-process it
(x_train, y_train), (x_test, y_test) = tf.keras.datasets.mnist.load_data()
x_train = x_train.reshape(-1, 784).astype("float32") / 255.0
x_test = x_test.reshape(-1, 784).astype("float32") / 255.0
# Limit the data to 1000 samples
x_train = x_train[:1000]
y_train = y_train[:1000]
x_test = x_test[:1000]
y_test = y_test[:1000]
כעת, הגדר התקשרות חוזרת מותאמת אישית פשוטה שמתעדת:
- כאשר
fit
/evaluate
/predict
התחלות & קצוות - מתי כל תקופה מתחילה ומסתיימת
- כאשר כל קבוצת אימון מתחילה ומסתיימת
- כאשר כל אצווה של הערכה (בדיקה) מתחילה ומסתיימת
- כאשר כל אצווה (תחזית) מתחילה ומסתיימת
class CustomCallback(keras.callbacks.Callback):
def on_train_begin(self, logs=None):
keys = list(logs.keys())
print("Starting training; got log keys: {}".format(keys))
def on_train_end(self, logs=None):
keys = list(logs.keys())
print("Stop training; got log keys: {}".format(keys))
def on_epoch_begin(self, epoch, logs=None):
keys = list(logs.keys())
print("Start epoch {} of training; got log keys: {}".format(epoch, keys))
def on_epoch_end(self, epoch, logs=None):
keys = list(logs.keys())
print("End epoch {} of training; got log keys: {}".format(epoch, keys))
def on_test_begin(self, logs=None):
keys = list(logs.keys())
print("Start testing; got log keys: {}".format(keys))
def on_test_end(self, logs=None):
keys = list(logs.keys())
print("Stop testing; got log keys: {}".format(keys))
def on_predict_begin(self, logs=None):
keys = list(logs.keys())
print("Start predicting; got log keys: {}".format(keys))
def on_predict_end(self, logs=None):
keys = list(logs.keys())
print("Stop predicting; got log keys: {}".format(keys))
def on_train_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Training: start of batch {}; got log keys: {}".format(batch, keys))
def on_train_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Training: end of batch {}; got log keys: {}".format(batch, keys))
def on_test_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Evaluating: start of batch {}; got log keys: {}".format(batch, keys))
def on_test_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Evaluating: end of batch {}; got log keys: {}".format(batch, keys))
def on_predict_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Predicting: start of batch {}; got log keys: {}".format(batch, keys))
def on_predict_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Predicting: end of batch {}; got log keys: {}".format(batch, keys))
בואו ננסה את זה:
model = get_model()
model.fit(
x_train,
y_train,
batch_size=128,
epochs=1,
verbose=0,
validation_split=0.5,
callbacks=[CustomCallback()],
)
res = model.evaluate(
x_test, y_test, batch_size=128, verbose=0, callbacks=[CustomCallback()]
)
res = model.predict(x_test, batch_size=128, callbacks=[CustomCallback()])
Starting training; got log keys: [] Start epoch 0 of training; got log keys: [] ...Training: start of batch 0; got log keys: [] ...Training: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 1; got log keys: [] ...Training: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 2; got log keys: [] ...Training: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 3; got log keys: [] ...Training: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] Start testing; got log keys: [] ...Evaluating: start of batch 0; got log keys: [] ...Evaluating: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 1; got log keys: [] ...Evaluating: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 2; got log keys: [] ...Evaluating: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 3; got log keys: [] ...Evaluating: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] Stop testing; got log keys: ['loss', 'mean_absolute_error'] End epoch 0 of training; got log keys: ['loss', 'mean_absolute_error', 'val_loss', 'val_mean_absolute_error'] Stop training; got log keys: ['loss', 'mean_absolute_error', 'val_loss', 'val_mean_absolute_error'] Start testing; got log keys: [] ...Evaluating: start of batch 0; got log keys: [] ...Evaluating: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 1; got log keys: [] ...Evaluating: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 2; got log keys: [] ...Evaluating: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 3; got log keys: [] ...Evaluating: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 4; got log keys: [] ...Evaluating: end of batch 4; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 5; got log keys: [] ...Evaluating: end of batch 5; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 6; got log keys: [] ...Evaluating: end of batch 6; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 7; got log keys: [] ...Evaluating: end of batch 7; got log keys: ['loss', 'mean_absolute_error'] Stop testing; got log keys: ['loss', 'mean_absolute_error'] Start predicting; got log keys: [] ...Predicting: start of batch 0; got log keys: [] ...Predicting: end of batch 0; got log keys: ['outputs'] ...Predicting: start of batch 1; got log keys: [] ...Predicting: end of batch 1; got log keys: ['outputs'] ...Predicting: start of batch 2; got log keys: [] ...Predicting: end of batch 2; got log keys: ['outputs'] ...Predicting: start of batch 3; got log keys: [] ...Predicting: end of batch 3; got log keys: ['outputs'] ...Predicting: start of batch 4; got log keys: [] ...Predicting: end of batch 4; got log keys: ['outputs'] ...Predicting: start of batch 5; got log keys: [] ...Predicting: end of batch 5; got log keys: ['outputs'] ...Predicting: start of batch 6; got log keys: [] ...Predicting: end of batch 6; got log keys: ['outputs'] ...Predicting: start of batch 7; got log keys: [] ...Predicting: end of batch 7; got log keys: ['outputs'] Stop predicting; got log keys: []
השימוש של logs
dict
logs
dict מכיל את הערך הפסד, וכל המדדים בסוף אצווה או עידן. הדוגמה כוללת את ההפסד ואת השגיאה המוחלטת הממוצעת.
class LossAndErrorPrintingCallback(keras.callbacks.Callback):
def on_train_batch_end(self, batch, logs=None):
print(
"Up to batch {}, the average loss is {:7.2f}.".format(batch, logs["loss"])
)
def on_test_batch_end(self, batch, logs=None):
print(
"Up to batch {}, the average loss is {:7.2f}.".format(batch, logs["loss"])
)
def on_epoch_end(self, epoch, logs=None):
print(
"The average loss for epoch {} is {:7.2f} "
"and mean absolute error is {:7.2f}.".format(
epoch, logs["loss"], logs["mean_absolute_error"]
)
)
model = get_model()
model.fit(
x_train,
y_train,
batch_size=128,
epochs=2,
verbose=0,
callbacks=[LossAndErrorPrintingCallback()],
)
res = model.evaluate(
x_test,
y_test,
batch_size=128,
verbose=0,
callbacks=[LossAndErrorPrintingCallback()],
)
Up to batch 0, the average loss is 30.79. Up to batch 1, the average loss is 459.11. Up to batch 2, the average loss is 314.68. Up to batch 3, the average loss is 237.97. Up to batch 4, the average loss is 191.76. Up to batch 5, the average loss is 160.95. Up to batch 6, the average loss is 138.74. Up to batch 7, the average loss is 124.85. The average loss for epoch 0 is 124.85 and mean absolute error is 6.00. Up to batch 0, the average loss is 5.13. Up to batch 1, the average loss is 4.66. Up to batch 2, the average loss is 4.71. Up to batch 3, the average loss is 4.66. Up to batch 4, the average loss is 4.69. Up to batch 5, the average loss is 4.56. Up to batch 6, the average loss is 4.77. Up to batch 7, the average loss is 4.77. The average loss for epoch 1 is 4.77 and mean absolute error is 1.75. Up to batch 0, the average loss is 5.73. Up to batch 1, the average loss is 5.04. Up to batch 2, the average loss is 5.10. Up to batch 3, the average loss is 5.14. Up to batch 4, the average loss is 5.37. Up to batch 5, the average loss is 5.24. Up to batch 6, the average loss is 5.22. Up to batch 7, the average loss is 5.16.
השימוש של self.model
תכונה
בנוסף לקבלת מידע יומן כשאחד שיטותיהם נקרא, יש הגיעו ליעדן גישה למודל הקשורים בסבב הנוכחי של אימונים / הערכה / היקש: self.model
.
הנה של כמה מן הדברים שאתה יכול לעשות עם self.model
ב התקשרות:
- סט
self.model.stop_training = True
לאימון פסיקה מיד. - Hyperparameters Mutate של האופטימיזציה (זמין כמו
self.model.optimizer
), כגוןself.model.optimizer.learning_rate
. - שמור את המודל במרווחי תקופה.
- רשום את הפלט של
model.predict()
על כמה דוגמאות מבחן בסוף כל תקופה, על מנת שישמש בדיקת שפיות במהלך האימונים. - חלץ הדמיות של תכונות ביניים בסוף כל תקופה, כדי לעקוב אחר מה שהמודל לומד לאורך זמן.
- וכו '
בואו נראה את זה בפעולה בכמה דוגמאות.
דוגמאות ליישומי התקשרות חוזרת של Keras
עצירה מוקדמת במינימום הפסד
מופעי דוגמא ראשונים זה יצירת Callback
שעוצרת אימונים כאשר המינימום של אובדן מוצה, על ידי הגדרת התכונה self.model.stop_training
(בוליאני). לחלופין, אתה יכול לספק ויכוח patience
כדי לציין כמה תקופות שאנחנו צריכים לחכות עד להפסקה לאחר הגיע מינימום מקומי.
tf.keras.callbacks.EarlyStopping
מספק יישום מלא יותר כללי.
import numpy as np
class EarlyStoppingAtMinLoss(keras.callbacks.Callback):
"""Stop training when the loss is at its min, i.e. the loss stops decreasing.
Arguments:
patience: Number of epochs to wait after min has been hit. After this
number of no improvement, training stops.
"""
def __init__(self, patience=0):
super(EarlyStoppingAtMinLoss, self).__init__()
self.patience = patience
# best_weights to store the weights at which the minimum loss occurs.
self.best_weights = None
def on_train_begin(self, logs=None):
# The number of epoch it has waited when loss is no longer minimum.
self.wait = 0
# The epoch the training stops at.
self.stopped_epoch = 0
# Initialize the best as infinity.
self.best = np.Inf
def on_epoch_end(self, epoch, logs=None):
current = logs.get("loss")
if np.less(current, self.best):
self.best = current
self.wait = 0
# Record the best weights if current results is better (less).
self.best_weights = self.model.get_weights()
else:
self.wait += 1
if self.wait >= self.patience:
self.stopped_epoch = epoch
self.model.stop_training = True
print("Restoring model weights from the end of the best epoch.")
self.model.set_weights(self.best_weights)
def on_train_end(self, logs=None):
if self.stopped_epoch > 0:
print("Epoch %05d: early stopping" % (self.stopped_epoch + 1))
model = get_model()
model.fit(
x_train,
y_train,
batch_size=64,
steps_per_epoch=5,
epochs=30,
verbose=0,
callbacks=[LossAndErrorPrintingCallback(), EarlyStoppingAtMinLoss()],
)
Up to batch 0, the average loss is 34.62. Up to batch 1, the average loss is 405.62. Up to batch 2, the average loss is 282.27. Up to batch 3, the average loss is 215.95. Up to batch 4, the average loss is 175.32. The average loss for epoch 0 is 175.32 and mean absolute error is 8.59. Up to batch 0, the average loss is 8.86. Up to batch 1, the average loss is 7.31. Up to batch 2, the average loss is 6.51. Up to batch 3, the average loss is 6.71. Up to batch 4, the average loss is 6.24. The average loss for epoch 1 is 6.24 and mean absolute error is 2.06. Up to batch 0, the average loss is 4.83. Up to batch 1, the average loss is 5.05. Up to batch 2, the average loss is 4.71. Up to batch 3, the average loss is 4.41. Up to batch 4, the average loss is 4.48. The average loss for epoch 2 is 4.48 and mean absolute error is 1.68. Up to batch 0, the average loss is 5.84. Up to batch 1, the average loss is 5.73. Up to batch 2, the average loss is 7.24. Up to batch 3, the average loss is 10.34. Up to batch 4, the average loss is 15.53. The average loss for epoch 3 is 15.53 and mean absolute error is 3.20. Restoring model weights from the end of the best epoch. Epoch 00004: early stopping <keras.callbacks.History at 0x7fd0843bf510>
תזמון קצב למידה
בדוגמה זו, אנו מראים כיצד ניתן להשתמש ב-Callback מותאם אישית כדי לשנות באופן דינמי את קצב הלמידה של האופטימיזציה במהלך האימון.
ראה callbacks.LearningRateScheduler
עבור הטמעות כלליות יותר.
class CustomLearningRateScheduler(keras.callbacks.Callback):
"""Learning rate scheduler which sets the learning rate according to schedule.
Arguments:
schedule: a function that takes an epoch index
(integer, indexed from 0) and current learning rate
as inputs and returns a new learning rate as output (float).
"""
def __init__(self, schedule):
super(CustomLearningRateScheduler, self).__init__()
self.schedule = schedule
def on_epoch_begin(self, epoch, logs=None):
if not hasattr(self.model.optimizer, "lr"):
raise ValueError('Optimizer must have a "lr" attribute.')
# Get the current learning rate from model's optimizer.
lr = float(tf.keras.backend.get_value(self.model.optimizer.learning_rate))
# Call schedule function to get the scheduled learning rate.
scheduled_lr = self.schedule(epoch, lr)
# Set the value back to the optimizer before this epoch starts
tf.keras.backend.set_value(self.model.optimizer.lr, scheduled_lr)
print("\nEpoch %05d: Learning rate is %6.4f." % (epoch, scheduled_lr))
LR_SCHEDULE = [
# (epoch to start, learning rate) tuples
(3, 0.05),
(6, 0.01),
(9, 0.005),
(12, 0.001),
]
def lr_schedule(epoch, lr):
"""Helper function to retrieve the scheduled learning rate based on epoch."""
if epoch < LR_SCHEDULE[0][0] or epoch > LR_SCHEDULE[-1][0]:
return lr
for i in range(len(LR_SCHEDULE)):
if epoch == LR_SCHEDULE[i][0]:
return LR_SCHEDULE[i][1]
return lr
model = get_model()
model.fit(
x_train,
y_train,
batch_size=64,
steps_per_epoch=5,
epochs=15,
verbose=0,
callbacks=[
LossAndErrorPrintingCallback(),
CustomLearningRateScheduler(lr_schedule),
],
)
Epoch 00000: Learning rate is 0.1000. Up to batch 0, the average loss is 26.55. Up to batch 1, the average loss is 435.15. Up to batch 2, the average loss is 298.00. Up to batch 3, the average loss is 225.91. Up to batch 4, the average loss is 182.66. The average loss for epoch 0 is 182.66 and mean absolute error is 8.16. Epoch 00001: Learning rate is 0.1000. Up to batch 0, the average loss is 7.30. Up to batch 1, the average loss is 6.22. Up to batch 2, the average loss is 6.76. Up to batch 3, the average loss is 6.37. Up to batch 4, the average loss is 5.98. The average loss for epoch 1 is 5.98 and mean absolute error is 2.01. Epoch 00002: Learning rate is 0.1000. Up to batch 0, the average loss is 4.23. Up to batch 1, the average loss is 4.56. Up to batch 2, the average loss is 4.81. Up to batch 3, the average loss is 4.63. Up to batch 4, the average loss is 4.67. The average loss for epoch 2 is 4.67 and mean absolute error is 1.73. Epoch 00003: Learning rate is 0.0500. Up to batch 0, the average loss is 6.24. Up to batch 1, the average loss is 5.62. Up to batch 2, the average loss is 5.48. Up to batch 3, the average loss is 5.09. Up to batch 4, the average loss is 4.68. The average loss for epoch 3 is 4.68 and mean absolute error is 1.77. Epoch 00004: Learning rate is 0.0500. Up to batch 0, the average loss is 3.38. Up to batch 1, the average loss is 3.83. Up to batch 2, the average loss is 3.53. Up to batch 3, the average loss is 3.64. Up to batch 4, the average loss is 3.76. The average loss for epoch 4 is 3.76 and mean absolute error is 1.54. Epoch 00005: Learning rate is 0.0500. Up to batch 0, the average loss is 3.62. Up to batch 1, the average loss is 3.79. Up to batch 2, the average loss is 3.75. Up to batch 3, the average loss is 3.83. Up to batch 4, the average loss is 4.37. The average loss for epoch 5 is 4.37 and mean absolute error is 1.65. Epoch 00006: Learning rate is 0.0100. Up to batch 0, the average loss is 6.73. Up to batch 1, the average loss is 6.13. Up to batch 2, the average loss is 5.11. Up to batch 3, the average loss is 4.57. Up to batch 4, the average loss is 4.21. The average loss for epoch 6 is 4.21 and mean absolute error is 1.61. Epoch 00007: Learning rate is 0.0100. Up to batch 0, the average loss is 3.37. Up to batch 1, the average loss is 3.83. Up to batch 2, the average loss is 3.80. Up to batch 3, the average loss is 3.50. Up to batch 4, the average loss is 3.31. The average loss for epoch 7 is 3.31 and mean absolute error is 1.42. Epoch 00008: Learning rate is 0.0100. Up to batch 0, the average loss is 5.33. Up to batch 1, the average loss is 4.84. Up to batch 2, the average loss is 4.02. Up to batch 3, the average loss is 3.87. Up to batch 4, the average loss is 3.85. The average loss for epoch 8 is 3.85 and mean absolute error is 1.53. Epoch 00009: Learning rate is 0.0050. Up to batch 0, the average loss is 1.84. Up to batch 1, the average loss is 2.75. Up to batch 2, the average loss is 3.16. Up to batch 3, the average loss is 3.52. Up to batch 4, the average loss is 3.34. The average loss for epoch 9 is 3.34 and mean absolute error is 1.43. Epoch 00010: Learning rate is 0.0050. Up to batch 0, the average loss is 2.36. Up to batch 1, the average loss is 2.91. Up to batch 2, the average loss is 2.63. Up to batch 3, the average loss is 2.93. Up to batch 4, the average loss is 3.17. The average loss for epoch 10 is 3.17 and mean absolute error is 1.36. Epoch 00011: Learning rate is 0.0050. Up to batch 0, the average loss is 3.32. Up to batch 1, the average loss is 3.02. Up to batch 2, the average loss is 2.96. Up to batch 3, the average loss is 2.80. Up to batch 4, the average loss is 2.92. The average loss for epoch 11 is 2.92 and mean absolute error is 1.32. Epoch 00012: Learning rate is 0.0010. Up to batch 0, the average loss is 4.11. Up to batch 1, the average loss is 3.70. Up to batch 2, the average loss is 3.89. Up to batch 3, the average loss is 3.76. Up to batch 4, the average loss is 3.45. The average loss for epoch 12 is 3.45 and mean absolute error is 1.44. Epoch 00013: Learning rate is 0.0010. Up to batch 0, the average loss is 3.38. Up to batch 1, the average loss is 3.34. Up to batch 2, the average loss is 3.26. Up to batch 3, the average loss is 3.56. Up to batch 4, the average loss is 3.62. The average loss for epoch 13 is 3.62 and mean absolute error is 1.44. Epoch 00014: Learning rate is 0.0010. Up to batch 0, the average loss is 2.48. Up to batch 1, the average loss is 2.38. Up to batch 2, the average loss is 2.76. Up to batch 3, the average loss is 2.63. Up to batch 4, the average loss is 2.66. The average loss for epoch 14 is 2.66 and mean absolute error is 1.29. <keras.callbacks.History at 0x7fd08446c290>
התקשרות חוזרת מובנית של Keras
הקפד לבדוק את ליעדן Keras קיים על ידי קריאת מסמכי API . היישומים כוללים כניסה ל-CSV, שמירת המודל, הדמיה של מדדים ב-TensorBoard ועוד הרבה יותר!